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Functions of Skeletal Functions of Skeletal System: System:11. . Support Support 2. 2. ProtectionProtection3.3.4. 4. Stores inorganic Stores inorganic materialsmaterials
Classification – bones Classification – bones classified by shape:classified by shape:
1. Long1. Long 2. 2. 3. 3. Flat Flat 4. 4. 5. Sesamoid5. Sesamoid
Structure of Long BoneStructure of Long Bone
Epiphysis- Epiphysis- Epiphyseal disk (line)-growth plateEpiphyseal disk (line)-growth plateDiaphysis- Diaphysis- Medullary cavity-hollow chamber in centerMedullary cavity-hollow chamber in centerSpongy bone- cancellous bone, found Spongy bone- cancellous bone, found mainly in epiphysismainly in epiphysisCompact bone-Compact bone-Periosteum-tough, vascular coveringPeriosteum-tough, vascular coveringEndosteum- membrance of bone forming Endosteum- membrance of bone forming cellscellsArticular cartilage-Articular cartilage-
Compact vs. Spongy Bone
• Perforating(Volkmann’s)
canal- Connects central
canals• Trabeculae-
• Canaliculi- canals btwn
osteocytes• Osteocyte-Bone cells• Lacunae-
Bone Development – 2 Types:
1. Intramembranous ossification (changing cartilage to bone) (ex. - skull)
• layers of undifferentiated connective tissue appear at sites of future bone
•
• osteoblasts become osteocytes (mature bone cells) when completely surrounded by a bony matrix
• Connective tissue on surface forms the periosteum
•
2. Endochondral ossification (remainder of skeleton)
• Hyaline cartilage models form at sites of future bone
• Cartilage cells degenerate over time
•
• osteoblasts become osteocytes when completely surrounded by a bony matrix
Bone Development
• In a long bone, hyaline cartilage is replaced by bony tissue in the center of the diaphysis first (primary ossification center)
• Bone develops from this point towards the end of the bone
•
Growth of Bones• Epiphyseal disk – area of
growth; separates epiphysisfrom diaphysis; 4 layers:1. Resting cells –
2. Reproducing cells - as they reproduce, they lengthen the bone
1.
Epiphyseal disk
1. Radial growth plate→
2. Fracture – distal
end of radius →
Digital growth
plate (in fingers)
(2 ½ yr. old)→
Fractures
• Greenstick-
• Fissuered- inc. longitudinal break
• Comminuted-complete, fragments bone
• Transverse-• • Oblique- complete at angle
other than right angle• Spiral-
Fracture Repair
• 4 stages– Blood escapes from blood
vessels and from hematoma.
– Spongy bone forms near blood vessels, fibrocartilage forms in distant regions (within days to weeks)
– Bony callus forms from cartilaginous callus similar to bone formation
– Osteoclasts remove excess bone to restore to original
Factors Affecting Bone Growth(Nutrients)
Deficiency Effect
Vit D (for Ca absorption)
Vit A (for osteoblast &osteoclast activity)
Vit C (for collagensynthesis)
Factors Affecting Bone Growth(Hormones)
Deficiency EffectPituitary growth Pituitary dwarfism hormone (excess – pituitary (stimulates cell division gigantism/acro-in the epi. disks) megaly)Thyroid hormone premature disk(stimulates cartilage ossification-growthreplacement in disk) stunted
Factors Affecting Bone Growth(Hormones & Exercise)
Deficiency EffectSex hormones stimulate ossifi-(cause growth of cation of disks;long bones; estrogen stop bone lengthstronger than androgen)Physical stress bone thins &
weak-(stimulates bone width; ens; atrophyhypertrophy)
2 divisions of skeleton:
1. Axial –
2. Appendicular –
pectoral & pelvic girdles, upper & lower limbs
Human Skeleton – composed of 206 bones (extra – sutural)
Surface Markings on Bone
• Surface of bones have various structural features for specific functions
• Depressions & Openings:ForamenMeatusSinus
Surface Markings on Bone
• Processes that Connective Tissue Attaches To:
Tuberosity
Spine
Trochanter
Crest
Process